<template>
  <div class="todo-footer">
    <label>
      <input type="checkbox" v-model="selectedAll" />
    </label>
    <span>
      <span>已完成{{ completedNum }}</span> / 全部{{ allNum }}
    </span>
    <button class="btn btn-danger" @click="deleteT" >清除已完成任务</button>
  </div>
</template>

<script>
export default {
  name: "Footer",
  props: ["todos","updateAll","deleteTodos"],
  methods: {
    deleteT() {
      this.deleteTodos();
    },
  },
  computed: {
    allNum() {
      return this.todos.length;
    },
    completedNum() {
      //方法一
      // return this.todos.filter(todo=>todo.comleted).length;
      //方法二
      return this.todos.reduce((pre, todo) => {
        if (todo.completed) {
          pre++;
        }
        return pre;
      }, 0);
    },
    selectedAll: {
      get() {
        return this.allNum > 0 && this.allNum === this.completedNum
      },
      set(val) {
        this.updateAll(val);
      }

    },
  },
};
</script>

<style>
/*footer*/
.todo-footer {
  height: 40px;
  line-height: 40px;
  padding-left: 6px;
  margin-top: 5px;
}

.todo-footer label {
  display: inline-block;
  margin-right: 20px;
  cursor: pointer;
}

.todo-footer label input {
  position: relative;
  top: -1px;
  vertical-align: middle;
  margin-right: 5px;
}

.todo-footer button {
  float: right;
  margin-top: 5px;
}
</style>
